Geophysics at Tintagel Castle: Non-invasive work ahead of the excavations

I am cheating on Day of Archaeology at little, as I am going to talk about work we at TigerGeo did in May, but that is being used to inform the very-much-happening-on-July-29th excavations at Tintagel Castle. We’ve been really excited to see the excavations progress over the last few weeks and can’t wait to get our hands on the reports and plans to go back to our own data with.


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Just getting the gear onto site was a challenge!

While there has been a lot of media attention about the excavations (see Sue’s excellent piece for the insider perspective), the geophysical surveys happened without much fanfare in May, in order to give us time to process the data and report it back to the dig team at CAU. We thought it might be interesting to have an insight into the work we did on site and the iterative process of interpreting, getting feedback and revisiting the data that we are engaged in. Most of the time, we don’t get such a great chance to see the excavations that follow our surveys so this is fantastic for us as we will be able to update our thinking and interpretations in detail.

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Magnetic Susceptibility readings being taken on the lower reaches of the southern terrace

So what did we get up to? The excavation team didn’t want to make such a drastic intervention on the site blind. They had target areas, based on what was already known or assumed about the site and asked us to look at them in more detail to allow them to better target their excavations. They were particularly interested in finding buildings from the post-roman period that had lain undisturbed by recent archaeologists, so they could look at them with fresh eyes and modern scientific methods. Any excavation is inherently destructive, and on sites as unique as Tintagel, it is important to minimise the impact of destructive research, so to help them do this we came up with a package of four complimentary methods:

  • Ground Penetrating Radar, which should be able to detect buried walls and surfaces
  • Earth Resistance Survey, which should detect the same things as the GPR, but using different properties of the material, giving us a ‘double chance’ to find them
  • Magnetic Susceptibility, a method that looks at how magnetisable a material is, telling us things about the presence of certain forms of iron. This can help distiguish between different activities taking place on site: we’d expect higher MS in areas of industry or settlement thanks to burning or heating, than we would in storage areas, for example
  • Terrestrial Laser Scanning, to produce highly detailed surface models to pin down the geophysical data but also very acurately located biulding platforms that had been recorded over the years by site archaeologists.

This isn’t a photograph, it’s part of the point cloud generated by the laser scanner. You can see the team on the right trying to stay out of the scan!

A lot of fun was had on site getting ourselves and our equipment into the right places. Unlike the dig team, because we had to be quite mobile, with heavy gear, we needed to use a rope-access team to provide safety lines for us, so there were a lot of logistics to contend with around making sure we could cover the right areas. We were on site for a total of about 8 days, and really enjoyed talking to visitors to the site about what we were doing and why: people were particularly interested in the laser scanner and we’ve had to edit a lot of tourists (and seagulls) out of our point clouds!


KC getting the scanner as far along the southern terrace as possible!

So what did we find out? The earth resistance and GPR surveys taken together confirmed the locations of some of the walls and floors that have subsequently been found in the trenches, and hinted that the archaeology on the southern terrace had a different character than that on the eastern area. The magnetic susceptibility data also suggested clear differences between the two areas, with low values on the eastern area and higher values with internal patterning on the southern terrace. This suggested to us that on the southern terrace people were living or working, using fire either for heat and cooking or for industrial purposes. We could also see come strong patches of enhancement that lay between what were thought to be buildings, so we suggested there may be one larger building here instead. The eastern area showed no settlement related enhancement. So were the buildings there perhaps storehouses? Many of the already excavated buildings in this area have been interpreted as stores rather than dwellings.

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Earth resistance underway (with ropes!) on the southern terrace

The laser scans were useful not only to us but to the excavation team as well as they will form the basis for the topographical data being collected about the site. We were able to use them to make important topographic corrections to our radar profiles, without which interpretation would have been very difficult!

GPR survey on the southern terrace: this is where one of the walls was found

GPR survey on the southern terrace: this is where one of the walls was found

So, what next? Well, our first and most exciting job is going to be to get all the plans and sections back in from the excavation team and see how they match up with our interpretation, especially of the radar: we were able to survey a larger area than could be excavated, so we can refine our interpretation based on the dig and better predict what other walls and floors lie on the southern terrace. Ideally, we’d like to come back and do even more radar and see if we can cover the entire southern terrace: this might give us the best chance of understanding the exciting structures there and their immediate context. We would also like to do more scanning to provide detailed topographic data for the entire islands. The Tintagel Research Project is set to continue, so watch this space….

You can see more photos from our work on facebook!

You wouldn't beleive how many of these we had to delete from the sky in our scans!

You wouldn’t beleive how many of these we had to delete from the sky in our scans!


Archaeology at Tintagel… on the edge of a cliff!

[I begin with two things – a confession and an apology. Firstly, the day I’ve chosen to describe in my Day of Archaeology isn’t actually the 29 July – as that day I was happily walking the south-west coast path and sitting on a beach in Cornwall. So I’ll be describing my day on Tuesday 26 July instead. Secondly, apologies as it’s being posted so late – the holiday is the reason for that too!]

Tuesday wasn’t a typical day in my role as Senior Properties Historian at English Heritage, but as I struggle to describe a typical day that’s nothing unusual. The day was spent at Tintagel Castle in Cornwall, where there are currently excavations being carried out by Cornwall Archaeology Unit, on our behalf. I drove down in the morning to meet a couple of TV crews – one from BBC Spotlight and another from the ITV local news, who had both been invited to cover the story of the excavations. After re-reading our press release and having a quick chat with our PR manager, I gave a couple of interviews about why we were carrying out the project, and took the crews up to the excavations to meet the archaeologists and show them the site.

Looking across to Tintagel Castle headland from the mainland.

Looking across to Tintagel Castle headland from the mainland.

I’ve been involved with Tintagel Castle for a couple of years, working on a complete overhaul of the interpretation and visitor information on site, alongisde various improvements to the cafe, shop and ticket points. We installed a new permanent exhibition in the visitor centre in 2015, and added a range of interpretation panels and artistic installations to the site at Easter 2016. My role was to carry out the historical and archaeological research, write the text, commission the reconstructions and models, and also to work alongside artists and interpretation colleagues to deliver the rest of the project.

The new exhibition at Tintagel installed in 2015.

The new exhibition at Tintagel installed in 2015.

So, what are we doing now at Tintagel? This is the first year of a five year research project which aims to find out more about the early medieval (post-Roman) settlement on the site. Occupied between the 5th and 7th centuries AD, this extraordinary defended site had somewhere in the region of 100 buildings scattered across the headland. It was linked to a trading network connecting it to the Mediterranean world – more imported amphora and fine tablewares, as well as fine glasswares, have been found at Tintagel than anywhere else in western Europe. We assume that this was an elite, possibly royal settlement, occupied perhaps by the rulers of the kingdom of Dumnonia. But there is much that we don’t understand – when exactly was the site occupied? What sort of activities were being carried out on site? Was it a seasonal settlement? What did the buildings look like? Were they stores, workshops or houses? Although excavations took place at Tintagel in the 1930s by C. A. Raleigh Radford, this was largely clearance work to display the building remains to the public and many of the records were lost when Radford’s Exeter house was bombed in the Second World War. A small amount of work was carried out in the 1990s by Glasgow University but it was restricted to the area already disturbed by Radford.

Site C, a range of buildings excavated by Radford in the 1930s and again by Glasgow University in the 1990s.

Site C, a range of buildings excavated by Radford in the 1930s and again by Glasgow University in the 1990s.

Cornwall Archaeology Unit (CAU) have been commissioned to carry out this research work which involves two seasons of excavations, plus post-ex analysis and publication following. This year’s archaeological work is an evaluation of two key areas of the site to establish the nature of the post-Roman remains and to identify one of the two areas for more in-depth archaeological work next year. The two areas were chosen as they were likely to preserve good archaeological stratigraphy and were undisturbed by medieval activity or later archaeological work. The first area is on the southern terrace where a small trench was opened as part of the Extreme Archaeology series in about 2003 – remember that? It had some dramatic footage of Alice Roberts dangling off a rope but actually the terrace is very accessible and not that scary to work on! The second area is on the eastern terraces, not far from the visitor steps up to the chapel area of the headland.

Whilst the TV crews were filming the archaeology and interviewing colleagues, I had a chance to look at the trenches for the first time. As I write the excavations are still ongoing, but early results look very interesting, with walls and areas of paving, and lots of finds including amphora fragments and pieces of glass.

Staff and volunteers from CAU hard at work in one of the southern terrace trenches.

Staff and volunteers from CAU hard at work in one of the southern terrace trenches.

Once the media interviews were over, I went up to the mainland courtyard to check on the set up for my talk to visitors. We have been hosting events for our visitors all week to tie into the excavations – regular talks from the site team in the morning and then a programme of talks from different specialists in the afternoon, as well as hands-on activities for children. Various staff and volunteers from CAU have also been on hand to talk to visitors about the archaeology at the trench edge. Of course, this is one of the busiest times of year being the summer holidays, so it takes quite a bit of time to get up and down the steps to the headland due to the sheer numbers of people – this narrow and steep route is the only way on and off the castle, at least for the time being!

My talk is entitled ‘Tintagel: where history meets legend’ which is also the title of the exhibition. I’m trying to explain to visitors how history and legend at Tintagel are completely intertwined – you can’t understand one without the other. My audience is typical for Tintagel visitors at this time of year – lots of families, children and a few attentive dogs. I try to explain how the site has became attached to the tradition of King Arthur and also introduce them to the other key legend at the site – the love story of Tristan and Iseult, and weave in the history of the site too. They all listen wonderfully and then I get lots of questions about the castle, the archaeology project and King Arthur. Various people come up afterwards to ask more questions about the site, including one teenager who wanted advice on becoming an archaeologist.

After a late lunch, I head back up to the castle to see how the panels and installations were being received by visitors – it is lovely to stand near a panel that you have written and hear people read it out to their children and see them engage with the sculptures and reconstructions.

An interpretation panel at Tintagel Castle

Visitors reading one of our new interpretation panels near the Great Hall. This one has the remains of a medieval feast in bronze on the top.

I also wanted to take some more photographs of the archaeology in action and speak to the volunteers. We had been planning to have lots of social media coverage but unfortunately broadband has been down at Tintagel for several days and there is no mobile signal, making it difficult to upload posts! Luckily one of the volunteers is a dab hand with photogrammetry and has made some brilliant 3D models of the trenches. He is also happily filming everyone with a handheld camcorder for the BBC’s Digging for Britain.

Unexpectedly I have a spare morning before my second talk to visitors tomorrow afternoon, and my offer to help in the trenches is seized upon by the team – luckily I have packed my trowel. It’s not often I get to actually do real archaeology – this will be a first in 11 years in the job!

Planning the trench - what a view!

Planning the second trench on the southern terrace – what a view!


Reconstructing a dolmen

Today is a busy one for me. I’m writing this on an overcrowded train to London on the first stage of a journey to the USA. It’s for pleasure not work, although as many archaeologists will tell you, at times the division is a blurry one.

For the past few months I’ve been working on a number of interesting projects. I have been working with Sustrust on the Giants Quoit project. For the last four years they have been working tirelessly with the Cornwall Council Historic Environment Service to excavate the site of Carwynnen Quoit near Camborne in Cornwall.

The dolmen (an entrance grave with three orthostats, or uprights, topped with a large flat capstone) fell down In 1842, and being a popular local landmark it was re-erected shortly afterwards. Unfortunately, in 1966, after an alleged earth tremor, it fell down once again. This time, the stones remained in a pile, and memories of the Quoit faded. In 2009 Sustrust bought the five acre field where the remains of the dolmen lay, and began to hatch plans to re-erect it.

My involvement came earlier this year, 2014, when I was asked to virtually reconstruct Carwynnen Quoit from existing laser scans of the individual stones and to investigate a number of other stones that had the potential to contain rock art. Armed with large quantities of 3D and excavation data and a number of historic photos from different angles, I busied myself with moving the modelled stones around on screen. One of the decisions made early on by the whole team was to reconstruct the quoit as it could have appeared thousands of years ago. Our historic images of the monument show the orthostats leaning at dangerous angles, having spent millennia being persuaded by gravity to cease trying to defy it, gradually tilting before collapsing.

Setting the stones upright by archaeologically studying the sockets in the ground and wear on the capstone meant that the Giants Quoit (as it is locally known) could stand again for, hopefully, millennia. It will never be exactly the same as the quoit was when originally built some 4500 years ago, but close, and importantly, safe, so that people can enjoy and engage with the monument.

I visited Carwynnen Quoit on a rainy day back at the beginning of May and it was a hive of activity. A school visit was in progress with a large marquee was set up as an outdoor classroom, with demonstrations of ancient technology such as honeysuckle rope construction, pottery, and theories about how the stones were originally moved. Lessons in poetry and art were planned for later in the day. I’m sure that day will have an influence on them for years to come – considering that local schools were also involved in the excavations of previous years, I wouldn’t be surprised if the seeds of a few embryonic archaeological careers haven’t been sown.

Using photogrammetry I made very detailed 3D models of the stones thought to contain rock art, and got a good feel for the site and how it may have appeared during the late Neolithic. We also crowded around the computer to continue to twist and move stones to help inform the reconstruction. It was decided to make a triangular wooden template to make sure that the orthostats would be positioned correctly.

Back at the office I processed the images of the rock art stones – the “Shield Stone” and “Coffin Stone” – into 3D point clouds and began to use a number of techniques to enhance details cut into the surface of the stones. I came to the conclusion that the marks on the Coffin Stone were mainly natural, although human-influenced, perhaps as a result of ploughing, dragging or even an attempt to dress it at some point. It is tempting to see a series of intersecting lines which form uneven diamond or lozenge patterns as deliberate, but they’re easily formed unintentionally.

The Shield Stone is interesting. The markings are deliberate, but I remain to be convinced that they were part of a singular design.

Photogrammetry of the reconstructed orthostats

Photogrammetry of the reconstructed orthostats

The 3D point clouds allow all kinds of analysis to take place that you cannot do physically, such as colouring the stone by depth to enhance details cut into the stone (they show up as a different colour to flatter parts) and removing distracting details such as the natural colours of the stone.

To match one of the historic photos of Carwynnen Quoit, an Edwardian picnic is being organised where participants will dress in period costume, eat lunch, and pose for a real plate photograph. Sadly, I’ve just had to reply to the invitation explaining that I’ll still be in the USA when it happens – I’d never normally turn away the opportunity for a ‘proper’ antiquarian day out!

Below are a few of the images that I created for the project. Visit the Giants Quoit website to find out more, and be sure to come back to the Day of Archaeology site to explore more of the amazing posts submitted today.


Simulated glass plate image of the 3D reconstruction




Laser scanned orthostats placed upon the excavation plan

Enhancing worn inscriptions and the Day of Archaeology 2012

My name is Tom Goskar and I am one of the organisers of the Day of Archaeology, as well as being a freelance archaeologist who specialises in applying digital techniques to different aspects of the discipline. My day today has been rather mixed, but predictably involved being at the proverbial digital coalface of archaeology in two aspects.

At 8am I checked my email to catch up with the behind-the-scenes talk between the eight organisers of the Day of Archaeology, and log into this website to begin moderating the posts that were by then flowing thick and fast. By 11am I had been on a Google Hangout with Pat and Jess, and we had re-jigged the homepage to make it easier to explore, as well as temporarily excluding posts from last year to highlight the new contributions. It looked much better afterwards. I have been dipping into the website on and off all day, making sure that posts looked good, and expanding and linking the occasional acronym to help readers know what they are. The DoA moderators have been hard at work in the engine room!

In between, for a personal project I have been processing 3D data from a medieval cross close to where I live, here in Penzance, Cornwall, as well as helping to refurbish a soon-to-be-open digital arts space in the town centre.

The Penzance Market Cross, made in the 11th century, is decorated and has many inscriptions. These are very eroded and most people do not notice them. Unless you happen to see the stone in just the right glancing sunlight, the sides of the cross appear to just have some panels of dots and a few lines, not much else. Nothing could be farther from the truth. Using photogrammetric techniques, I have been examining the cross to see if how well 3D capture techniques can enhance the inscriptions and decorations, with the aim of comparing my results with drawings made using traditional techniques (rubbings, chalking, torchlit photos).

In the spirit of the Day of Archaeology, below is a working illustration showing the north east elevation of the Market Cross, which I produced for this blog post. In the centre of the image is the cross as the casual visitor may see it. To the left, the colour information has been removed (which can sometimes be distracting), leaving the shape of the stone artificially coloured grey, with a virtual light source moved to show some of the decoration. To the right, a Radiance Scaling shader has been applied, which colours concavities and convexities to help reveal details on the stone.

Penzance Market Cross

Penzance Market Cross, captured in 3D with photogrammetry, and enhanced using digital filters.


As you can see from the Radiance Scaling image to the right, there is definitely more going on than first meets the eye. The figure in the second panel from the top is clearly visible, as are the letters and glyphs in the lower two panels. As I type, I am processing a mesh with a much higher level of detail, and look forward to the results which will be ready in the early hours of tomorrow morning. Comparing the results to the accepted interpretations made by Professor Charles Thomas will be interesting, whether they differ or help to confirm what we already know.

So, my Day of Archaeology has been a busy and varying one, and it’s not over yet. Time to publish this post, and return to the list of posts to publish some more from around the globe, so that we can all show to the world what archaeologists really get up to in our own words. I hope that it helps people today and in the future to understand just how exciting and relevant archaeology is to us all.

You can follow my archaeology musings over at my blog Past Thinking.